Paper and paperboard are produced from an aqueous slurry of cellulosic fiber, depositing this slurry on a moving papermaking wire or fabric, and forming a sheet from the solid components of the slurry by draining the water. This sequence is followed by pressing and drying the sheet to further remove water.
Drainage or dewatering of the fibrous slurry on the papermaking wire or fabric is often the limiting step in achieving faster paper machine speeds. Improved dewatering can also result in a drier sheet in the press and dryer sections, resulting in reduced energy consumption. Chemicals are often added to the fibrous slurry before it reaches the papermaking wire or fabric to improve drainage/dewatering and solids retention; these chemicals are called papermachine retention and/or drainage aids.
Dry strength additives are used in paper mill to increase the strength of paper. It increases the strength of paper by increasing internal bond formation. Moreover dry strength additives improve bust strength, tear strength, wax pick values, folding endurance, stiffness, machine runnability, increase levels of paper filler uses etc. Dry strength additives also reduced linting and dusting. A drainage aid may also provide improved dry strength on a papermachine, where an increase in drainage is utilized to increase refining or dilute the headbox consistency, thus providing improved sheet strength properties.
Papermachine drainage aids have reduced efficacy in some furnish substrates which contain high levels of soluble organics and salts. Two such examples of these furnishes are neutral sulfite semi-chemical (NSSC) and kraft virgin linerboard, where high levels of soluble lignin and other organic materials containing a high anionic charge are present. These highly anionic materials neutralize the charge on the conventional drainage and dry strength aids, significantly reducing their effectiveness.